Signal Conditioning

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trigger detect glitch




I'm not sure if this post is suppose to go here as its not so much a question.  I wanted to put up this weird problem I bumped into with an older version of LabVIEW (8.0) using the basic level trigger detection to prevent other people from running into this anomalous behavior.


My goal was to detect an overshoot in a waveform that resembles a square wave. I decided to use two basic level trigger detect VIs in sequence to detect certain rising and falling points in the square wave.  However, the first detection would work and the second one wouldn't. 


What I determined was that the levels could not be the same magnitude (even if different signs).  For example, if I used 2000 lbf for a rising edge and -2000 lbf for a falling edge the last VI in the sequence would not function correctly ( possibly some memory and logic problem with the DLL call ) 


The solution was to make sure that the magnitudes were different. So if I used 2000 lbf for the first trigger detect, I had to use something like -2050 lbf for the second trigger detect.  Pretty strange problem so I thought I should post it here since I couldn't find anything resembling my problem.  It could be that in the newer versions, 8.6 and up, that this issue has been resolved. 

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Hello tavak,


Thank you for posting this. What card are you using to detect your overshoot? can you post your code here as well so I can try and replicate this issue.


-Nathan H

Software Developer
National Instruments
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Thanks for quick reply, looks like it was a mistake on my end as I'm unable to recreate the problem and in fact it seems to work just fine.  I'm guessing I had some sort of race condition going or some faulty logic but the trigger detection is working flawlessly. Sorry for the confusion.



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